This invention relates to a heat exchanger applied to a vaporizer of a fuel cell system for example.
In a fuel cell system using a reformer, alcohol and water are vaporized in a heat exchanger and supplied to a reformer in the form of gaseous mixture in order to generate hydrogen gas which is supplied to the fuel cell system.
Tokkai Hei 9-79694 published by the Japanese Patent Office in 1997 discloses a heat exchanger which vaporizes a mixture of two types of liquid. In this heat exchanger, a gaseous mixture of ammonia and water is produced from an ammoniacal solution.
When vaporizing a mixture of two liquids with a single heat exchanger, the mixing ratio of the liquid mixture must be varied in order to vary the mixing ratio of components in the gaseous mixture. In such a heat exchanger, however, when the mixing ratio of the liquid mixture is varied, the mixing ratio of the gaseous mixture will not coincide with a target ratio until the liquid which remains inside the heat exchanger is completely vaporized. In this type of heat exchanger, response characteristics related to control of the mixing ratio are low.
Use of a plurality of heat exchangers for independently vaporizing different kinds of fluid and a mixer for mixing the different kinds of vaporized fluid may improve the response characteristics related to control of the mixing ratio. In a fuel cell system for a vehicle, however, it is difficult to obtain a space for accommodating a plurality of heat exchangers.
It is therefore an object of this invention to increase the control characteristics on the mixing ratio of a plurality of liquids when using a single heat exchanger.
In order to achieve the above object, this invention provides a heat exchanger which performs heat exchange between a high temperature fluid and a low temperature fluid. The heat exchanger comprises a heat exchanging portion comprising a first fluid passage allowing flow of a first low temperature fluid, and a second fluid passage partitioned from the first fluid passage and allowing flow of a second low temperature fluid. The heat exchanger further comprises a first supply mechanism which supplies the first low temperature fluid to the first fluid passage, and a second supply mechanism which supplies the second low temperature fluid to the second fluid passage.
This invention also provides a heat changer comprising a heat exchanging portion comprising a water passage allowing flow of water, an alcohol passage allowing flow of alcohol, and a high temperature fluid passage for heating the water passage and the alcohol passage. The high temperature fluid passage comprises a high temperature section having a contact with the water passage, and a low temperature section having a lower temperature than the high temperature section and having a contact with the alcohol passage. The heat exchanger further comprises a water supply mechanism supplying water to the water passage, and an alcohol supply mechanism supplying alcohol to the alcohol passage.